using System;
using System.Numerics;

public class Program
{
    public static void Main()
    {
        //int num = int.Parse(Console.ReadLine() ?? string.Empty);
        string[] str = (Console.ReadLine() ?? string.Empty).Trim().Split(' ');
        //string str = Console.ReadLine() ?? string.Empty;
        

        BigInteger a = BigInteger.Parse(str[0]);
        BigInteger b = BigInteger.Parse(str[1]);

        BigInteger c = a ^ b;

        Console.WriteLine(c);
    }
}